Lack of general work experience; lack of business experience and/or training; lack of management (people and project) experience; inability to speak or present confidently to a group; little or no understanding of the customer or market; and many more…
Lack of domain knowledge, micromanaging, or lack of willingness to take a stance. Startups need someone decisive, who knows the field, and lets their employees get shit done.
You are somewhat contradicting yourself- why do you need deep domain knowledge if you let your employees get shit done?
That isn't a contradiction. You need domain knowledge to know which problems to prioritize, in order to converse with customers, and generally to not look like an idiot. Customers will not trust the company if its own CEO doesn't understand the space.
I would also add that it’s important for a boss to know how to do the job of his or her reports, mostly because in order to judge performance you need to know what goes into doing a good job. If you don’t want to get ripped off by your mechanic, you need to know a thing or two about cars, and the same is true for software.
My main filter is the same as my BS filter, assuming they otherwise have basic competence and at least one strong leadership quality.